Releasing czlib and zstd Go Bindings

At GopherCon US 2016, cgo bindings for two compression libraries, czlib and zstd, were released. These libraries have been used in production at Datadog. The performance of these libraries varies significantly depending on the interface used. Benchmark results show that using a non-streaming interface in czlib can be faster than the standard library's compress/zlib for both compression and decompression. Zstd, developed by Yann Collet, is a fast compression library with similar performance to zlib but with much faster decompression times. The zstd Go binding mimics the zlib interface and supports advanced features like stream compression, compression levels, and pre-computed dictionaries.